Skid control braking systems are becoming increasingly available for tractor trailers utilized in the transportation of commerce over roadways throughout the world. The skid control braking systems represent significant improvement in safety for tractor trailers. In some of the braking systems, spring brake systems are utilized to prevent unintended movement of the trailer when parked.
Other braking systems provide skid control utilizing single channel skid control systems wherein a plurality of speed sensors associated with wheels on each side of the vehicle generate a wheel speed signal. Based on the wheel speed signals, the skid control systems control the braking of the wheels. In the past, such skid control systems have been added to pre-existing spring brake systems of the trailer braking system. Consequently, the resulting systems included a number of discreet component valves which were fitted separately to the trailer and were individually connected to separate electrical and air lines.
As a result, the valve assemblies were beset with many shortcomings including:
a) the separate valves required complex and time consuming installation; PA0 b) due to the lack of available space on the vehicle or trailer, the valves had to be mounted in various locations making assembly difficult and troubleshooting cumbersome; PA0 c) the separate valves required the use of special air reservoirs which were very expensive; PA0 d) utilizing so many valves necessitated the use of many expensive connectors which often caused significant line resistance and air leaks; PA0 e) an inordinate amount of costly pneumatic tubing was required to interconnect the valves of the devices; and, PA0 f) the multiple components and additional tubing led to costly installation, maintenance and repair problems, aggravated by wear and failure of the excessive tubing requirements.